Universal-Serial-Bus (USB) has been widely deployed as a standard bus for connecting peripherals such as digital cameras and music players to personal computers (PCs) and other devices. Currently, the top transfer rate of USB is 480 Mb/s, which is quite sufficient for most applications. Faster serial-bus interfaces are being introduced to address different requirements. PCI Express, at 2.5 Gb/s, and SATA, at 1.5 Gb/s and 3.0 Gb/s, are two examples of high-speed serial bus interfaces for the next generation devices, as are IEEE 1394 and Serial Attached Small-Computer System Interface (SCSI).
FIG. 32(A) shows a prior-art peripheral-side USB connector. USB connector 10 may be mounted on a board in the peripheral. USB connector 10 can be mounted in an opening in a plastic case (not shown) for the peripheral.
USB connector 10 contains a small connector substrate 14, which is often white ceramic, black rigid plastic, or another sturdy substrate. Connector substrate 14 has four or more metal contacts 16 formed thereon. Metal contacts 16 carry the USB signals generated or received by a controller chip in the peripheral. USB signals include power, ground, and serial differential data D+, D−.
USB connector 10 contains a metal case that wraps around connector substrate 14. The metal case touches connector substrate 14 on three of the sides of connector substrate 14. The top side of connector substrate 14, holding metal contacts 16, has a large gap to the top of the metal case. On the top and bottom of this metal wrap are formed holes 12. USB connector 10 is a male connector, such as a type-A USB connector.
FIG. 32(B) shows a female USB connector. Female USB connector 20 can be an integral part of a host or PC, or can be connected by a cable. Another connector substrate 22 contains four metal contacts 24 that make electrical contact with the four metal contacts 16 of the male USB connector 10 of FIG. 32(A). Connector substrate 22 is wrapped by a metal case, but small gaps are between the metal case and connector substrate 22 on the lower three sides.
Locking is provided by metal springs 18 in the top and bottom of the metal case. When male USB connector 10 of FIG. 32(A) is flipped over and inserted into Female USB connector 20 of FIG. 32(B), metal springs 18 lock into holes 12 of male USB connector 10. This allows the metal casings to be connected together and grounded.
Flash-memory cards are widely used for storing digital pictures captured by digital cameras. One useful format is Sony's Memory Stick (MS), having a small form factor roughly the size of a stick of chewing gum. Another highly popular format is Secure-Digital (SD), which is an extension of the earlier MultiMediaCard (MMC) format. SD cards are relatively thin, having an area roughly the size of a large postage stamp. In addition, SD cards come in a variety of “flavors” including micro-SD cards, which have only eight pins.
SD cards are also useful as add-on memory cards for other devices, such as portable music players, personal digital assistants (PDAs), and even notebook computers. SD cards are hot-swappable, allowing the user to easily insert and remove SD cards without rebooting or cycling power. Since the SD cards are small, durable, and removable, data files can easily be transported among electronic devices by being copied to an SD card. SD cards are not limited to flash-memory cards. Other applications such as communications transceivers can be implemented as SD cards.
The SD interface currently supports a top transfer rate of 100 Mb/s, which is sufficient for many applications. However, some applications such as storage and transport of full-motion video may benefit from higher transfer rates.
Other bus interfaces offer higher transfer rates. Universal-Serial-Bus (USB), for example, has a top transfer rate of 480 Mb/s. Peripheral-Component-Interconnect (PCI) Express, at 2.5 Gb/s, and Serial-Advanced-Technology-Attachment (SATA), at 1.5 Gb/s and 3.0 Gb/s, are two examples of high-speed serial bus interfaces for next generation devices. IEEE 1394 (Firewire) supports 3.2 Gb/s. Serial Attached Small-Computer System Interface (SCSI) supports 1.5 Gb/s. These are roughly 5 to 32 times faster than the SD interface.
What is needed is a flexible system that supports both standard Universal-Serial-Bus (USB) devices and one or more secondary flash memory devices (e.g., micro-Secure Digital (micro-SD) cards) using a single (e.g., either standard USB or special dual-personality) socket. In particular, what is needed is that serves as an interface between a host system and the secondary flash memory devices (e.g., a micro-SD card) by way of the special dual-personality socket.